One known type of information storage device is a disk drive device that uses magnetic media to store data and a movable read/write head that is positioned over the media to selectively read from or write to the disk.
Consumers are constantly desiring greater storage capacity for such disk drive devices, as well as faster and more accurate reading and writing operations. Thus, disk drive manufacturers have continued to develop higher capacity disk drives by, for example, increasing the density of the information tracks on the disks by using a narrower track width and/or a narrower track pitch. However, each increase in track density requires that the disk drive device have a corresponding increase in the positional control of the read/write head in order to enable quick and accurate reading and writing operations using the higher density disks. As track density increases, it becomes more and more difficult using known technology to quickly and accurately position the read/write head over the desired information tracks on the storage media. Thus, disk drive manufacturers are constantly seeking ways to improve the positional control of the read/write head in order to take advantage of the continual increases in track density.
FIG. 1 illustrates a conventional disk drive unit and shows a magnetic disk 101 mounted on a spindle motor 102 for spinning the disk 101. A voice coil motor arm 104 carries a head gimbal assembly (HGA) that includes a slider 103 incorporating a read/write head (sometimes having an associated micro-actuator). A voice-coil motor (VCM) is provided for controlling the motion of the motor arm 104 and, in turn, controlling the slider 103 to move from track to track across the surface of the disk 101, thereby enabling the read/write head to read data from or write data to the disk 101. Hard disk drives also typically include an upper and lower magnet located proximate to the end of the VCM (e.g., at the actuator fan tail portion). This design generally offers good TMR (Track MisRegistration) performance, higher servo bandwidth, and reduction of torsion and/or bending forces related to asymmetric magnetic forces.
Unfortunately, however, the upper and lower magnet configuration suffers from several drawbacks, as well. For example, one drawback of this design approach relates both to the cost of an additional magnet, as well as the cost of the discarded magnetic material that is wasted during the manufacturing process. This problem sometimes becomes even more of an issue when the disk drive form factor is reduced, because a reduction in the form factor also increases the amount of wasted magnetic material compared to the actual material that is used in the product. Therefore, a design inefficiency is introduced.
One hard disk drive has been built in large quantities that implements a single magnet design. However, this disk drive design was unique to the disk drive industry because it included a single head, with a single arm that was mounted to an unsupported rotating shaft. This design approach suffers from many drawbacks. For example, this approach generally is unable to achieve higher servo bandwidth, suffers poor TMR, lacks a good rotary vibration performance, etc. These drawbacks, taken individually and/or in combination, unfortunately produce lower storage capacities and poor overall performance for the resulting disk drive device. Other attempts to develop single magnet designs have been unsuccessful, because they have required increased power consumption and have provided lower seek performance.
Thus, it will be appreciated that there is a need in the art for improved voice coil motors, and methods of making the same.